1. Field
The present invention relates generally to data communication, and more specifically to techniques for allocating uplink resources in a multiple-input multiple-output (MIMO) communication system, which may advantageously utilize channel state information (CSI) and may further employ successive cancellation (SC) receiver processing to provide improved system performance.
2. Background
Wireless communication systems are widely deployed to provide various types of communication such as voice, data, and so on, for a number of users. These systems may be based on code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), or some other multiple access techniques.
A multiple-input multiple-output (MIMO) communication system employs multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. In one common MIMO system implementation, the NT transmit antennas are located at and associated with a single transmitter system, and the NR receive antennas are similarly located at and associated with a single receiver system. A MIMO system may also be effectively formed for a multiple access communication system having a base station that concurrently communicates with a number of terminals. In this case, the base station employs a number of antennas and each terminal may employ one or more antennas.
A MIMO channel formed by the NT transmit and NR receive antennas may be decomposed into NC independent channels, with NC≦min {NT, NR}. Each of the NC independent channels is also referred to as a spatial subchannel of the MIMO channel and corresponds to a dimension. The MIMO system can provide improved performance (e.g., increased transmission capacity) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.
The available resources for uplink transmissions from the terminals to the base station are limited. Typically, only a fraction of the terminals may be scheduled for transmission on the available spatial subchannels, which may be limited by the number of antennas employed at the base station. Each “possible” spatial subchannel between a terminal and the base station typically experiences different link characteristics and is associated with different transmission capability. Efficient use of the available uplink resources (e.g., higher throughput) may be achieved if the available spatial subchannels are effectively allocated such that data is transmitted on these subchannels by a “proper” set of terminals in the MIMO system.
There is therefore a need in the art for techniques to allocate uplink resources in a MIMO system to provide improved system performance.